Ultra-wideband antenna

ABSTRACT

An ultra-wideband antenna is formed from a coaxial cable passed through the center of a conductive tube. The center conductor of the coaxial cable is connected to an end of the conductive tube, and the shield of the coaxial cable is not electrically connected to any conductor. Two ferrite beads are disposed serially on the cable beneath the tube, spaced apart from the tube and spaced apart from one another. A centering spacer maintains the coaxial cable within the center of the tube.

REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/934,801 titled “1P Antenna,” which is in incorporated hereinby reference.

BACKGROUND AND SUMMARY

In one embodiment, an antenna according to the present disclosure isconfigured to be recessed into an underground enclosure, such as a watermeter pit. A mushroom-shaped housing partially extends above the coverof the pit. In another embodiment, the antenna can be mounted aboveground. The ultra-wideband antenna is formed from a coaxial cable passedthrough the center of a conductive tube. The center conductor of thecoaxial cable is connected to an end of the conductive tube, and theshield of the coaxial cable is not electrically connected to anyconductor. Two ferrite beads are disposed serially on the cable beneaththe tube, spaced apart from the tube and spaced apart from one another.A centering spacer maintains the coaxial cable within the center of thetube.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be better understood with reference to the followingdrawings. The elements of the drawings are not necessarily to scale,emphasis instead being placed upon clearly illustrating the principlesof the disclosure. Furthermore, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 depicts an antenna according to an exemplary embodiment of thepresent disclosure.

FIG. 2 depicts an antenna for use in underground pits.

FIG. 3 is a partially cut-away view of a partial antenna assemblyaccording to the embodiment of the present disclosure discussed abovewith respect to FIG. 1.

FIG. 4 is a partially cut-away view of a partial antenna assemblyaccording to the embodiment of the present disclosure discussed abovewith respect to FIG. 1.

FIG. 5 is a partially cut-away view of the antenna of FIG. 2.

FIG. 6 is a partially cut-away view of a partial antenna assemblyaccording to another embodiment of the present disclosure.

FIG. 7 is a partially cut-away view of an antenna according to anotherembodiment of the present disclosure.

FIG. 8 is a representation of the distal end of the coaxial cable of anantenna.

DETAILED DESCRIPTION

FIG. 1 depicts an antenna 100 according to an embodiment of the presentdisclosure. The antenna 100 comprises a coaxial cable 105 extendingthrough a tube 101. The tube 101 is a thin, conductive, cylindricaltube, formed from brass in the illustrated embodiment. (The tube 101 asillustrated is partially cut-away to show the coaxial cable 105 withinthe tube 101.) In one embodiment, the tube 101 has an outside diameterof 0.75 inches and is 42.6 millimeters long. The wall of the tube isbetween 0.38 mm and 0.420 mm thick in one embodiment.

The tube 101 has a distal end 107 and a proximal end 108. A center wire102 of the coaxial cable 105 is electrically connected to the tube 101.A shield 103 of the coaxial cable 105 terminates below distal end 107 ofthe tube 101 in the illustrated embodiment and is not electricallyconnected to any conductor at the distal end of the cable 105. In oneembodiment, the coaxial shield 103 terminates ¼ inches below distal end107 of the tube 101. In one embodiment, the coaxial shield 103terminates between 6.1 mm and 6.6 mm from the distal end 107 of the tube101. In one embodiment, a dielectric insulator (not shown) of thecoaxial cable extends above the shield 103 of the coaxial cable 105 andterminates before the center wire 102 is connected to the tube 101.

The coaxial cable 105 is substantially centered within the tube 101. Acentering spacer 110 keeps the coaxial cable 105 centered within thetube 101 for substantially the length of the tube 101. At the distal end107 of the tube, the center wire 102 is bent and electrically connectedto the tube 101. The centering spacer 110 is formed from an insulatingmaterial. In one embodiment, the centering spacer 110 is formed frompolyurethane foam.

A first ferrite bead 104 and a second ferrite bead 106 are disposed onthe cable 105 beneath the proximal end 108 of the tube 101. The ferritebeads 104 and 106 extend around the shield 103 of the cable 105. In oneembodiment, the first ferrite bead 104 is spaced from the proximal end108 of the tube 101 a distance of between 84.8 mm and 87.6 mm. In oneembodiment, the second ferrite bead 106 is spaced from the first ferritebead 104 a distance of between 59 mm and 61 mm. The spacing of the firstand second ferrite beads 104 and 106 is designed to affect the resonantpoint of the antenna 100. A connector 111 at the end of the cable 105connects the antenna 100 into a system (not shown).

FIG. 2 depicts an antenna 200 according to an embodiment of the presentdisclosure. The antenna 200 comprises a mushroom-shaped housing 201configured to be used in underground pits, such as a water meter pit.The housing 201 is formed from a nylon composite material in theillustrated embodiment. The housing 201 comprises a rounded top portion208 unitarily formed with a threaded portion 202. The threaded portion202 is substantially cylindrical with continuous threads along an outersurface for receiving a threaded nut 203. The rounded top portion 208 iscircular when viewed from the top and extends outwardly from thethreaded portion 202. The threaded portion 202 may be fit within anopening (not shown) on a cover (not shown) of a water meter (not shown),for example, and the rounded top portion 208 is larger than the openingand the threaded portion and thus remains above the top of the cover andabove ground when installed. The threaded nut 203 secures the antenna200 to the cover. The antenna 200 can operate when installed in eithermetal or composite covers.

A coaxial cable 205 extends downwardly from a bottom of the housing 201as shown. A first ferrite bead 204 and a second ferrite bead 206 aredisposed on the cable 205 beneath the housing 201. The ferrite beads 204and 206 are substantially the same as the ferrite beads 104 and 106discussed above with respect to FIG. 1. The housing 201 houses the tube101 discussed above, and the coaxial cable 205 is substantially the sameas the coaxial cable 105 discussed above.

A waterproof connector 207 is disposed on the cable 205 beneath thesecond ferrite bead 206. Additional cable length 209 extends on theother side of the connector 207.

FIG. 3 is a partially cut-away view of a partial antenna assembly 300according to the embodiment of the present disclosure discussed abovewith respect to FIG. 1. In this partial assembly 300, the centeringspacer 110 has been installed on the coaxial cable 105. A threadedflange 313 is disposed on the cable 105 between the distal end of thecable 105 and the first ferrite bead 104. The threaded flange 313comprises an opening (not shown) that receives the cable 105. Thethreaded flange 313 is not rigidly affixed to the cable but can moveupward and downward with respect to the cable 105. The threaded flange313 has exterior threads that mate with threads (not shown) interior tothe housing 201 (FIG. 2). As discussed further with respect to FIG. 5below, the threaded flange 313 thus threadably mates with the bottom endof the housing 201.

A stopper 311 is rigidly affixed to the cable 105 between the distal endof cable 105 and the threaded flange 313. The stopper 311 prevents thethreaded flange 313 from moving on the cable 105 when the threadedflange is threaded into the housing 201 (FIG. 2). Although the threadedflange 313 is spaced apart from the stopper 311 in FIG. 3, the threadedflange 313 rests against the stopper 311 when the threaded flange isscrewed into the housing 201.

A flexible seal 312 is compressed between the threaded flange 313 andthe stopper and forms a water-resistant seal. In the illustratedembodiment, the seal 312 is an O-ring.

FIG. 4 is a partially cut-away view of a partial antenna assembly 400according to the embodiment of the present disclosure discussed abovewith respect to FIG. 1. In this partial assembly 400, the conductivetube 101 has been added to the partial assembly 300 (FIG. 3). The centerwire 102 of the cable 105 has been bent over the tube 101 andelectrically connected to the tube 101. The centering spacer 110 fitswithin the tube 101 and serves to keep the cable 105 centered within thetube 101 for most of the length of the tube 101. In this regard, forgenerally at least 75% of the length of the tube, the cable 105 iscentered within the tube before it is bent over to the tube wall. Thecentering spacer also serves to keep the tube 101, which is verythin-walled, mechanically stable. The centering spacer 110 has anopening to receive the cable 105. The outside diameter of the centeringspacer 110 is slightly smaller than the inside diameter of the tube 101.

FIG. 5 is a partially cut-away view of the antenna 200 of FIG. 2.Importantly, the tube 101 extends above into the rounded top portion 208a distance “d” as shown. This is important because the rounded topportion 208 is generally above ground when the antenna is in use, andthe tube 101 generally needs to extend above ground in order for theantenna to transmit properly. In one embodiment, the distance “d” isbetween 0.40 and 0.49 inches.

The threaded flange 313 is engaged within the housing 202. In thisregard, external threads on the threaded flange 313 mate with internalthreads (not shown) within the threaded portion 202 of the housing 201.

FIG. 6 is a partially cut-away view of a partial antenna assembly 600according to another embodiment of the present disclosure. Thisembodiment may be used above the ground. In this embodiment the innerworkings of the antenna are substantially identical to the antennasdiscussed herein, but the housing is configured differently. In thispartial assembly 600, the centering spacer 110 has been installed on thecoaxial cable 105. A threaded flange 613 is disposed on the cable 105between the distal end of the cable 105 and the first ferrite bead 104.The threaded flange 613 comprises an opening (not shown) that receivesthe cable 105. The threaded flange 613 is not rigidly affixed to thecable but can move upward and downward with respect to the cable 105.The threaded flange 613 has exterior threads that mate with threads (notshown) interior to the housing, as further discussed below with respectto FIG. 7.

A stopper 611 is rigidly affixed to the cable 105 between the distal endof cable 105 and the threaded flange 613. The stopper 611 prevents thethreaded flange 613 from moving on the cable 105 when the threadedflange is threaded into the housing 701 (FIG. 7). Although the threadedflange 613 is spaced apart from the stopper 611 in FIG. 6, the threadedflange 613 rests against the stopper 611 when the threaded flange isscrewed into the housing 701.

A flexible seal 612 is compressed between the threaded flange 613 andthe stopper 611 and forms a water-resistant seal. In the illustratedembodiment, the seal 612 is an O-ring. In some embodiments, atear-shaped flexible seal 620 is used to maintain a spacing of the cable105 within the threaded portion of the threaded flange 613.

FIG. 7 is a partially cut-away view of an antenna 700 that may be usedabove the around. A partial assembly of the antenna 700 was discussedabove with respect to FIG. 6. The threaded flange 613 is engaged withinthe housing 701. In this regard, external threads on the threaded flange613 mate with internal threads (not shown) within the housing 201. Insome embodiments, the threaded flange 613 mates with mounting hardware(not specifically shown) when attaching the antenna—for example, theantenna 700 shown in FIG. 7—to a metal or composite cabinet or an‘L’-shaped metal bracket used for remote pole mounting.

FIG. 8 is a representation of the coaxial cable 105 of an antenna 100 asdiscussed herein with respect to FIG. 1. The antenna is a half wave endfed configuration at the lowest operating frequency and at allharmonics, such as would commonly referred to as a “non-resonant end fedantenna.” The name derives from the fact that the feed line is actuallypart of the radiating element of the antenna after exiting the ferritebead 104 (FIG. 1). The coaxial cable 105 is represented in rough crosssection by three lines in FIG. 8: line 801 is the center conductor andlines 802A and 802B are the shield. Although coaxial cables aretypically considered as having two conductors, at radio frequencies coaxactually has three conductive surfaces: the center conductor 801; theinside surface 803 of the shield (braid) 802A; and the outside surface804 of the shield 802A. The center conductor 801 of the coaxial cableand the inside surface 803 of the shield comprises the feed line andcarries the signal in the direction indicated by directional arrow 810along its length to the load (common mode currents). When the RF signalreaches the end of the coax, the currents on the center conductor 801and the inside surface 803 of the shield cancel each other andsubstantially no radiation is generated. The application of theconductive tube 101 (FIG. 1) surrounding the cable 105 as discussedherein causes the RF energy to wrap around from the inside surface 803of the shield and begin to flow on the outside surface 804 of the shieldback toward the load, in the direction indicated by directional arrow811. This current flowing on the outside of the shield does not canceland begins to radiate.

In order for a half wave end fed configuration to perform properly atthe lowest operating frequency and at all harmonics, the RF current mustnot travel back to the transceiver (not shown). Therefore the radiatingshield current must be prevented from continuing down the feed line,while allowing the internal feed currents to continue unaffected. Theferrite beads 104 and 106 (FIG. 1) around the outer shield of thecoaxial cable 105 limit the effect on the transceiver and the intendedresonant point (resonant frequency) of the antenna. The limitations ofthe current create an end fed antenna.

The antenna broadband tuning is accomplished automatically by theaddition of the tube 101 (FIG. 1) placed over and around the end of theradiating element with the center coax conductor 102 attached to thedistal end 107 of the tube as described and shown herein. The antennadoes not require a ground plane or the necessity for retuning, unlikemany other antennas, and is vertically polarized.

When the operating frequency varies, the antenna resonance isautomatically changed due to the reaction of the inductive andcapacitive reactance maintained between the two over a broad bandwidth.As frequency decreases below resonance and the antenna becomesinductive, this tuning network offsets this reactive shift, therebystabilizing voltage standing wave ratio (VSWR). Once the frequencyincreases above resonance and becomes capacitive, the same tuningnetwork offsets this reactive shift, continuing to stabilize VSWR.

The antenna has a wide bandwidth an is suitable for cellular, IOT,Wi-Fi, and Bluetooth applications deployed in various environments.

What is claimed is:
 1. An ultra-wideband antenna comprising: a coaxialcable extending through the center of a conductive tube, a distal end ofa center conductor of the coaxial cable electrically connected to adistal end of the conductive tube, a distal end of a shield of thecoaxial cable not electrically connected to any conductor; a first and asecond ferrite bead disposed on the coaxial cable outwardly from aproximal end of the conductive tube, outside of the conductive tube, thefirst and second ferrite bead disposed serially on the coaxial cable,spaced apart from one another.
 2. The antenna of claim 1, furthercomprising a centering spacer disposed between the conductive tube andthe coaxial cable, the centering spacer configured to maintain thecoaxial cable substantially centered within the conductive tube.
 3. Theantenna of claim 2, wherein the centering spacer is formed from aninsulating material.
 4. The antenna of claim 3, wherein the centeringspacer is formed from polyurethane foam.
 5. The antenna of claim 1,wherein the conductive tube is formed from brass, and wherein a wall ofthe tube is between 0.38 mm and 0.420 mm thick.
 6. The antenna of claim1, wherein the shield of the coaxial cable terminates within theconductive tube, a distance of between 6.1 mm and 6.6 mm from the distalend of the conductive tube.
 7. The antenna of claim 1, wherein the firstferrite bead is spaced from a proximal end of the conductive tube bybetween 84.8 mm and 87.6 mm.
 8. The antenna of claim 7, wherein thesecond ferrite is spaced apart from the first ferrite bead by a distanceof between 59 mm and 61 mm.
 9. The antenna of claim 1, wherein each ofthe first and second ferrite beads extends around the outer shield ofthe coaxial cable, and wherein the first and second ferrite beads areconfigured to affect a resonant point of the antenna.
 10. The antenna ofclaim 1, further comprising a mushroom-shaped housing configured to beinstalled in a lid of an underground pit, the housing comprising arounded top portion unitarily formed with a male-threaded portion, themale-threaded portion configured to pass through an opening in the lid,the rounded top portion configured to extend above the lid.
 11. Theantenna of claim 10, wherein the conductive tube extends into therounded top portion a distance of between 0.40 and 0.49 inches.
 12. Theantenna of claim 10, further comprising a female-threaded nut configuredto mate with the male-threaded portion of the housing and secure thehousing to the lid.
 13. An ultra-wideband antenna comprising: aconductive tube comprising a distal end and a proximal end; a coaxialcable extending through the center of the conductive tube, the coaxialcable comprising a center conductor and a shield, a distal end of thecenter conductor electrically connected to the distal end of theconductive tube; a first and a second ferrite bead disposed on thecoaxial cable outwardly from the proximal end of the conductive tube,outside of the conductive tube, the first and second ferrite beaddisposed serially on the coaxial cable, spaced apart from one another.14. The antenna of claim 13, a distal end of a shield of the coaxialcable not electrically connected to any conductor.
 15. The antenna ofclaim 13, further comprising an insulating centering spacer disposedbetween the conductive tube and the coaxial cable, the centering spacerconfigured to maintain the coaxial cable substantially centered withinthe conductive tube.
 16. The antenna of claim 13, further comprising amushroom-shaped housing configured to be installed in a lid of anunderground pit, the housing comprising a rounded top portion unitarilyformed with a male-threaded portion, the male-threaded portionconfigured to pass through an opening in the lid, the rounded topportion configured to extend above the lid.
 17. The antenna of claim 16,wherein the conductive tube extends into the rounded top portion adistance of between 0.40 and 0.49 inches.
 18. The antenna of claim 16,further comprising a female-threaded nut configured to mate with themale-threaded portion of the housing and secure the housing to the lid.19. An ultra-wideband antenna comprising: a conductive tube comprising adistal end and a proximal end; a coaxial cable extending through thecenter of the conductive tube, the coaxial cable comprising a centerconductor and a shield, a distal end of the center conductorelectrically connected to the distal end of the conductive tube; and aninsulating centering spacer disposed between the conductive tube and thecoaxial cable, the centering spacer configured to maintain the coaxialcable substantially centered within the conductive tube.
 20. The antennaof claim 19, further comprising a first and a second ferrite beaddisposed on the coaxial cable outwardly from the proximal end of theconductive tube, outside of the conductive tube, the first and secondferrite bead disposed serially on the coaxial cable, spaced apart fromone another.